Car mounted hand brake mechanisms are well known in the railway industry. These hand brake mechanisms are normally mounted at one end of the railway car, remotely from the truck mounted braking system and typically include a hand wheel that is used to rotate a gear wheel to apply the brakes, and a housing having a back wall and a front wall, with a chain winding drum and a main gear wheel rotatably mounted on the housing.
A hand wheel shaft is also rotatably mounted on the housing and has a bearing section at one end and a hand wheel receiving section on the other end external to the housing. A ratchet wheel is rotatable with the shaft intermediate the ends of the shaft and a pawl is provided which cooperates with the ratchet wheel so as to prevent reverse rotation of the ratchet wheel. A freely rotatable pinion on the shaft engages the main gear wheel, the pinion having a radially extending flange cooperating therewith. A disengageable driving connection is provided between the radially extending flange and the ratchet wheel.
A trip cam is rotatably mounted in the housing and a trip bar, operable by the trip cam, cooperates with the radially extending flange to move the flange to disengage the driving connection and permit the pinion to freely rotate the main gear wheel for rotation in a brake releasing direction, accompanied by release of the chain winding drum and a chain wound on the chain winding drum to release the railway car handbrake.
The main gear wheel and chain winding drum comprise a main gear assembly, having a circular gear plate with gear teeth about its periphery, a central passageway through the gear plate, for mounting on a shaft, and a substantially square chain drum upon which the chain is wound.
The square chain drum has a longitudinal axis with a reduced diameter trunion at one end that is secured in the central passageway of the main circular gear plate. A shaft bore is provided through the square chain drum along its longitudinal axis and a drum shaft is mounted with a first end journaled in a back wall of the housing, such that the main gear assembly is freely rotatably mounted on the drum shaft. The front wall of the housing preferably has an upper section, an intermediate section extending outwardly away from the back wall, and a lower section extending downwardly from the intermediate section, with the drum shaft extending between the back wall and the lower section of the front wall.
The chain is typically coupled to a truck mounted braking system. One type of such truck mounted braking system is one which is commonly referred to as a TMX.RTM. truck mounted braking system (TMX.RTM. is a registered trademark of Westinghouse Airbrake Technologies, the assignee of the present invention). In this type system the chain is connected to the lever disposed within TMX.RTM. braking system for applying brake pressure through a series of linkages and levers.
Requirements for European railway industry hand brake mechanisms differ in that these mechanisms are mounted within the truck bogie (Axle Motion III) and thus become integral with the truck mounted braking system. These requirement further mandates that hand brake mechanisms are to be spatially confined to the envelope of the truck bogie.